SOLID Design Principles
A quick reference to writing Scalable, Maintainable, and Flexible OO Code
When building large-scale applications that need to stand the test of time, having a flexible and adaptable codebase is essential. A well-structured architecture helps ensure that the software remains scalable and easy to maintain as it grows. SOLID is a set of five core design principles in object-oriented programming that guide developers in writing cleaner, more maintainable, and flexible code. By following these principles, you can make smarter architectural decisions that lead to more robust and efficient software.
SOLID Design Principles Single Responsibility Principle (SRP) states that a class should have only one reason to change, or in simpler terms, a class should do only one thing and do it well.
In the code below, the left side shows a violation of SRP, while the right side presents the correct implementation.
Open/Closed Principle (OCP) states that software entities — classes or modules, should be open for extension but closed for modification. You should be able to add a new functionality without changing the existing code. This is one of the common coding practices implemented using interfaces.
In the code below, the left side shows a violation of OCP, while the right side presents the correct implementation.
Liskov Substitution Principle (LSP) states that subtypes must be substitutable for their base types without altering the correctness of the program. Subclass should be able to replace its parent class without breaking the program’s behavior.
In the code below, the left side shows a violation of LSP, while the right side presents the correct implementation.
Interface segregation principle (ISP) states that no code should be forced to depend on methods it does not use. A large interface is split into small and specific interfaces so that only clients can only implement the interfaces that they are interested in.
In the code below, the left side shows a violation of ISP, while the right side presents the correct implementation.
Dependency Inversion Principle (DIP) states that high-level modules should not depend on low-level modules. It encourages us to depend on interfaces or abstract classes rather than concrete classes. This makes the code more flexible and easier to maintain & avoid tight coupling.
I hope this article serves as a quick reference to help you understand these principles and apply them to write cleaner, more maintainable, and scalable code.”
Happy Coding !